Devastating impacts of global warming that threaten humanity are a pushback from Nature under assault, UN chief Antonio Guterres warned Sunday ahead of a key climate conference.

Air pollution forced the closure of schools and universities in parts of Iran on Saturday, including Tehran, which was cloaked by a cloud of toxic smog, state media reported.

The decision to shut schools and universities in the capital was announced late Friday by deputy governor Mohammad Taghizadeh, after a meeting of an emergency committee for air pollution.

Campaigners were preparing to occupy a vast opencast coal mine in eastern Germany on Saturday to put pressure on the government to phase out the fossil fuel -- a divisive issue in the country's rust belt.

Spain wanted to make a splash on the international scene by agreeing to host next month's COP25 climate summit at the last minute after Chile pulled out. 

Two men trying to cross the Arctic Ocean on skis have run into difficulty as unusually thin ice has lengthened their journey and cut into their rations, their team said Saturday.

A third of the species of tropical plants in Africa are potentially threatened with extinction, according to a preliminary estimate published Wednesday by the journal Science Advances.

Switching to renewables could cut the health impacts of air pollution from power generation as much as 80 percent by mid-century, experts said Tuesday.

Lightning strikes killed at least 18 people and injured several more during a deadly night in Pakistan's Thar desert, police said Friday, describing the deaths as "unprecedented".

Another exceptional high tide swamped flood-hit Venice on Friday, prompting the mayor to order St Mark's square closed after Italy declared a state of emergency for the UNESCO city.

Football legend Didier Drogba helped launch a drive Friday to plant a million trees to halt deforestation in Ivory Coast.